measuring passive crossover

[jayam000]

I want to measure frequency response of passive crossover by using PC.
Kindly let me know what software & hardware will be better for this .

[Loren42]

Originally Posted by jayam000

I want to measure frequency response of passive crossover by using PC.
Kindly let me know what software & hardware will be better for this .

Software: HolmImpulse would do it and it is free.

For a sound card the M-Audio MobilePre would be nice, but your PC sound car may be fine. If you use a PC sound card and an electret mic you need phantom power of some kind.

You can buy a calibrated mic here. They have a calibrated and uncalibrated version.

Then you need a book on how to do it.

You will find this a tricky thing to do and I suggest reading that book and any other material you can get to help you understand how and why.

[jayam000]

Thanks Loren42.But i don't understand why Mic is required to measure frequency response of only passive crossover separately.

[Loren42]

Originally Posted by jayam000

Thanks Loren42.But i don't understand why Mic is required to measure frequency response of only passive crossover separately.

Because the end result you are trying to measure is the frequency response of the system, which includes driver and cabinet.

Measuring the crossover only is a useless endeavor because the loads at the crossover (speaker drivers) are reactive, not resistive. Remember, a speaker driver's voice coil is inductive and therefore not measured as resistance, but impedance. There is an important difference.

Also, the cabinet will also impact the driver's impedance, so you need to include that in the chain of measurements. That is why you use a mic to measure the system.

Lastly, measuring the response of a speaker system is also riddled with problems like reverberations and reflections of the acoustic wave from walls and the floor in the room. So measurement techniques are important and get kind of complicated. HolmImpulse has a gating feature to help with that, but that is only useful down to about 200 to 400 Hz (depending on the room and how you have your system set up). You must use other techniques to get the response below that.

I am assuming you are trying to dial in the crossover or at least quantify an existing crossover's operation. Since all the components (drivers, crossovers, and box) are interdependent, you need to consider the whole thing as a system.

[Inductor]

Originally Posted by jayam000

Thanks Loren42.But i don't understand why Mic is required to measure frequency response of only passive crossover separately.

Following logic, the xover works with a complementary driver(s). So you want to measure xover with a driver (mic). If not, (if this is what you need simulated) you need only the electrical output of the xover (not good for any driver in special), assuming constant impedance/inductance.

[freddi]

that might be useful in conjunction with (but not in place of) system measurements to check tolerances or find a defective cap

[jayam000]

Thanks Loren42, Inductor & freddi,
I got it what u say.What u say is perfect.
But here i want to make crossover for for my friend who is away from my place.
I am just going to make compression driver crossover for him.
So i asked about testing procedure without mic.

[jayam000]

I have seen this Paudio crossover design.
There is 3.3 ufd capacitor & 33 ohm resistor in parallel.
Kindly let me know why this is used?
The rest is -12 db crossover with 4.7 ufd & .65 mh coil as i think.
The company have given this circuit with PH2380 horn.
So if we need to make good crossover over for compression driver than it must be with horn to be used.

[Loren42]

Originally Posted by jayam000

I have seen this Paudio crossover design.
There is 3.3 ufd capacitor & 33 ohm resistor in parallel.
Kindly let me know why this is used?
The rest is -12 db crossover with 4.7 ufd & .65 mh coil as i think.
The company have given this circuit with PH2380 horn.
So if we need to make good crossover over for compression driver than it must be with horn to be used.

I am unclear what compression driver you are designing to. If it is the one with the schematic you posted, just build what they cited and be done with it. Measurement is meaningless without a driver hooked up to it anyway.

If that is not the driver, then you need to start over from scratch and from what little I know about compression drivers, those crossovers are more complex than simple tweeters because the compression driver frequency response is usually not very linear and the horn that is attached to it also changes that response curve.

If it were me I would try to find a crossover schematic for the driver (either from the driver manufacture or a speaker that uses it) and build that. The only good that can come out of measuring the crossover without the driver (but you still need to put in a resistive load to test it) is to find out if you have an out of spec or bad component. You can do the same thing by measuring each component with an LCR meter, too, and it requires less effort.

[Michael Chua]

Originally Posted by jayam000

I have seen this Paudio crossover design.
There is 3.3 ufd capacitor & 33 ohm resistor in parallel.
Kindly let me know why this is used?
The rest is -12 db crossover with 4.7 ufd & .65 mh coil as i think.
The company have given this circuit with PH2380 horn.
So if we need to make good crossover over for compression driver than it must be with horn to be used.

The 3.3uF//33 ohm is a CD Horn EQ. Without it, it will sound "Honky".

If you change the compression driver or the horn, you will likely need to do some adjustment to this network. You will need a mic and some software to do a frequency sweep.